There is also a large set of algorithms for adversarial search problems, such as playing board games, that traditionally don't use machine learning. Minimax is

There is also a large set of algorithms for adversarial search problems, such as playing board games, that traditionally don't use machine learning. Minimax is the simplest one, and then there are negamax, alpha-beta pruning, negascout, etc. I believe Stockfish (the world's strongest chess program, or close to it) has actually improved its evaluation function using machine learning, but this is a fairly recent development.